1. Field of the Invention
The present invention relates to a print apparatus, a method of controlling the print apparatus, a storage medium and a cartridge.
2. Description of the Related Art
In an electrophotographic print apparatus, such as a color LBP (Laser-Beam Printer), 4 series drum type electro-photographic engines are now normally used. In such print apparatuses, upon color printing all of the photosensitive drums associated with the yellow, magenta, cyan and black cartridges, in contact with a sheet or a sheet conveyance belt, are rotated to develop a color image. On the other hand, upon monochrome printing, only the photosensitive drum associated with the black cartridge, in contact with a sheet or the sheet conveyance belt, is rotated to develop a monochrome image.
However, an electro-photographic engine using common drum control upon color and monochrome printing is known. Upon monochrome printing, printing is performed without moving the photosensitive drums for color printing away from the belt. According to this technique, the number of driving parts required to move the photosensitive drums away from the belt can be reduced and the structure can be simplified, thereby cost a reduction can be realized.
Further, in a print job based on mixed data of color data and monochrome data much time is required for switching between color print mode and monochrome print mode when the photosensitive drums are moved away from the belt, as it takes time to move the drums. However, in the above structure where the photosensitive drums for color printing are not moved away from the belt even upon monochrome printing, the reduction of printing speed due to the print mode switching processing can be suppressed.
However, in the above case where the photosensitive drums for color printing are not moved away from the belt even upon monochrome printing wear and tear can be caused to the parts related to these photosensitive drums, as the photosensitive drums for the colors not used in the printing, i.e., yellow, magenta and cyan colors, are also rotated.
As described above, in the 4 series drum type of electro-photographic engine, the cost, the speed and the lifetime are closely correlated. It is important to determine the apparatus configuration while maintaining the balance among these factors. For example, it is known to calculate the wear and tear when all the pages of an original are to be printed in color mode and when monochrome pages are printed in monochrome mode; and to perform printing in which ever one of the color mode or the monochrome mode which produces the lower degree of wear and tear (see Japanese Patent Laid-Open No. 2000-29266 (D1)). According to this technique, it is possible to suppress wear and tear of the drum or the like by controlling the switching between the color mode and the monochrome mode.
Further, the wear and tear of the drum which occurs upon printing also occurs in print post processing. Accordingly, it is known to accurately determine the lifetime of a photosensitive drum in consideration of the wear and tear during print post processing (see Japanese Patent Laid-Open No. 7-325517 (D2)).
When a printing apparatus which does not move the photosensitive drums away during printing is used, the photosensitive drums for yellow, magenta and cyan colors are more seriously worn in color printing than they are in monochrome printing. However, in actual fact, the printing apparatus does not make distinction between wear and tear on photosensitive drums during color printing and monochrome printing. There is no difference in wear and tear on rollers and gears between processing to form an image on the photosensitive drum and processing which does not result in an image being formed on the photosensitive drum, since rotating the rollers and the gears for rotation of the photosensitive drum are rotated upon printing in each case. However, the occurrence/non-occurrence of charging and the degree of abrasion of the drum surface differ between a case where an image is formed on the photosensitive drum and a case where no image is formed on the photosensitive drum. Accordingly, the wear and tear of the photosensitive drum when image formation is performed on the photosensitive drum and that when image formation is not performed on the photosensitive drum are different from each other. For example, when the print apparatus is used mainly for the purpose of facsimile printing, the frequency of monochrome printing is high and that of color printing is low. Conventionally, there is no distinction between the wear and tear of the photosensitive drum during color printing and during monochrome printing. In the above case where monochrome printing is mainly performed, even though the lifetime of the photosensitive drum for color printing is not actually expired, it is determined that the lifetime of the photosensitive drums for color printing or cartridges having the photosensitive drums has expired when the lifetime of the photosensitive drum for monochrome printing has been expired.
The above-described conventional technique D1 proposes a method for suppression of the wear and tear on consumable parts. To suppress wear and tear on the consumable part, a control method is proposed in which a choice is made regarding moving the drum away. However, this control method cannot solve the problem in the structure where the drums are not moved away.
Further, the above-described conventional technique D2 discloses the accurate calculation of wear and tear on the drum in consideration of wear and tear in post processing of printing in addition to wear and tear on the drum during printing. However, this method of calculating the wear and tear on a drum does not take into consideration the difference in wear and tear of the drum for color printing and for monochrome printing.